1. Field of Invention:
This invention relates generally to devices for treating cancer, and more particularly to an applicator for this purpose which synergistically combines the positive effects of hyperthermia and chemotherapy to destroy cancerous lesions.
2. Status of Prior Art:
It has long been recognized that by heating a malignant tumor to a higher temperature than that of tissues surrounding the tumor whose temperature is at normal body temperature, this action destroys the tumor. The effectiveness of such hyperthermia depends on the fact that cancers have poor circulation and a reduced ability to dissipate heat. Thus a temperature of no more than 115 degrees Fahrenheit is capable of destroying cancer cells while sparing healthy tissues.
The 1987 U.S. Pat. No. 4,398,537 to Guibert discloses a hyperthermia technique for destroying a malignant tumor whose site in the body of an individual is within an internal region underlying the surface of the skin. Applied to the surface of the skin is a stream of air which is heated to produce an air wave having periodic pulses whose peak temperature is well-above body temperature, the intervals between these pulses being at an air temperature just above body temperature.
As a consequence, heat from the high temperature pulses in the stream of air flowing over the surface of the skin is conductively transferred from the skin during the lower-temperature intervals to the tumor in the internal region below the skin, thereby raising the temperature of the tumor to a level which destroys it. But because the skin surface is subjected to relatively long low-temperature intervals between the high-temperature pulses, the cooling which takes place during these intervals results in a skin temperature which is never raised to an unsafe degree.
Also of prior art interest is the 1995 Guibert et al. U.S. Pat. No. 6,554,487. This patent discloses a combined chemo-thermo therapy technique in which a pharmaceutical agent, such as a lipolysis cream, is topically applied to a localized skin surface overlying a problem region to be treated. This surface is then subjected to an air stream whose temperature alternates periodically from a high peak level to a lower base level in a pulsatory heat energy wave pattern. Because heat transfer takes place under the skin in the intervals between successive peaks, the temperature of the problem region containing the tumor is significantly raised, but that on the skin surface remains at a tolerable level. As a consequence, the absorption of the agent and its diffusion throughout the tissue of the heated problem region is accelerated and its interaction therewith is promoted to enhance the effectiveness of the treatment.
The concern of the present invention is with the treatment of cancerous lesions disposed in an internal region of the body that is not accessible to hyperthermic apparatus of the type disclosed in the above-identified Guibert patents in which a stream of heated air is applied to a skin area overlying an internal region having a malignant tumor therein.
Typical of a region which is not accessible to the prior Guibert apparatus is the colon, for should there be malignant tumors on the mucosa of the colon, one could not then destroy these tumors by applying pulsed heat to a skin area of the body. The site of the colon in the body is so distant from the skin surface, that if a stream of heated air were applied to this skin surface, the heat in the course of its transfer from the skin surface to the colon would be dissipated in the intervening tissues of the body, and would never reach the colon.
The colon is a large intestine extending from the cecum to the rectum. Although the colon is a continuous hollow muscular tube, it is divided into several sections, namely the ascending colon, the transverse colon and the descending colon. As it enter the pelvis, the colon makes a double curve similar to the letter S, this being known as the sigmoid colon. The end of the sigmoid colon terminates at the rectum. The rectum and the colon constitute a meandering passage having a tubular membrane. In order therefore for an applicator or other device to reach a remote site in the tubular membrane of the colon, the applicator must snake its way through the passage. Thus a flexible fiberoptic sigmoidoscope can make its way well into the colon to detect cancerous tissues.
In the United States, the colon and rectum account for more cancer cases each year than any other anatomic site, other than the lungs. The primary treatment for colon cancer consists of a surgical resection of the lesions. But surgical treatment for colon cancer is not a permanent cure and often does not prevent a recurrence of the cancer.
According to the Merck Manual (15.sup.th Edition, page 819), chemotherapy has not proven to be effective as a surgical adjuvant in clinical trials of colon and rectal cancers. And studies of adjuvant radiation therapy, after curative cancer surgery, indicate that such radiation only delays the recurrence of the cancer.